1. Field of the Invention
The present invention relates to a brake control apparatus mounted on a vehicle.
2. Description of Related Art
JP-A-7-89432 discloses a brake pressure boosting apparatus for a vehicle. In the brake pressure boosting apparatus, brake pressure is boosted to a higher level during braking operation executed in a panic situation than that in a normal situation so as to apply higher brake pressure to wheel cylinders. That is, by amplifying a driver's brake pedal stroke or depressing force with a larger assisting ratio of a brake booster than an assisting ratio under the normal operation thereof, higher brake pressure is attained to generate at a master cylinder .
In general, the larger reaction force from a brake pedal is, the larger burden of a driver becomes when the driver depresses the brake pedal further resisting this reaction force. Therefore, it is difficult for the driver to depress the brake pedal further under a panic situation or the like due to this burden. In the conventional brake pressure boosting apparatus, because the assisting ratio of the brake booster is just increased in a panic situation, the driver's burden caused by reaction force from the brake pedal can not be lightened. Thus, when a female or an elderly driver is in charge of the brake pedal depression to the conventional brake pressure boosting apparatus, even though the driver intends to obtain higher braking force, it is difficult for the driver to obtain the same.
Further, when the driver depresses the brake pedal in order to pull the vehicle up to his targeted point, he can depress the brake pedal strongly only in an initial braking operation before he begins to feel reaction force from the brake pedal. However, if reaction force receiving from the brake pedal becomes large due to the fact that it was strongly depressed down, the driver is apt to release the depressing of the brake pedal more or less against his wish to stop the vehicle. This could happen in a braking situation close to an urgent braking. In this instance, the driver can only obtain a lower braking force than expected. As a result, the distance required before the stoppage of the vehicle is prone to lengthen with respect to his targeted point against his estimation.